Monday, 30 March 2020

D is for Dune slacks

Please remember! We ask that people do not visit the Reserve particularly if you have to travel. All car parks on Holy Island are closed to visitors until government restrictions are lifted. Many residents on Holy island fall into the vulnerable category. Please adhere to these guidelines for the health and safety of yourself and others during this time.

Amongst the rolling sand dunes and rustling marram grass of Lindisfarne National Nature Reserve there is a rare habitat where specialist plants and invertebrates thrive – dune slacks.

Humid dune slacks are a component of most large, dynamic dune systems. They are damp or wet hollows left between dunes where the groundwater reaches or approaches the surface of the sand. The seasonally fluctuating water table usually reaches a maximum in winter and spring and drops in summer. They are mostly found in large dune systems in the west of the UK where rainfall totals are significantly higher. This makes Lindisfarne National Nature Reserve the most important site for this habitat in the whole north-east of the UK.

Nutrient levels within these slacks is generally low. This helps deter the establishment of competing plants and results in high species diversity. Rare plant species can become established such as Petalwort – a type of bryophyte which can be found on Lindisfarne National Nature Reserve.

Species rich - humid dune slack on Lindisfarne NNR

We manage these areas by clearing scrub that will otherwise succeed. If left, scrub succession will reduce species diversity and extract valuable water. Surveying and monitoring of these important plant communities is routinely carried out to ensure that the management is being successful.

Another tool we use to monitor the slacks is hydrological monitoring. Using dipwells we can monitor the water table levels and test whether there has been any saltwater intrusion into the slacks. As sea levels rise with climate change, this will become more of a threat. Saltwater intrusion will turn the water briny and fundamentally change the plant communities that are able to survive.

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